1. Field of the Invention
The present invention relates to a swash plate type compressor, and more particularly to a swash plate type compressor in which compressed refrigerant is smoothly discharged.
2. Description of the Related Art
In a typical air conditioning system for a vehicle, refrigerant compressed by a compressor is condensed by a condenser and transferred to an expansion valve. The expansion valve makes the refrigerant in form of wet saturated vapor of low temperature and low pressure, and transfers the wet saturated vapor to an evaporator. The evaporator performs heat exchange between the low temperature refrigerant and the outside air so that the refrigerant absorbs the heat of the outside air. Then, the evaporator transfers the refrigerant to the compressor so that the above cycle is repeated.
The compressor used to compress the refrigerant in the air conditioning system for a vehicle sucks the refrigerant vaporized in the evaporator, compresses the sucked refrigerant, and discharges the compressed refrigerant, so that the refrigerant can continuously circulated. The compressor can be classified into a plurality of types such as a swash plat type, a scroll type, a rotary type, and a wobble plate type, according to a driving method.
The swash plate type compressor includes a cylinder having a plurality of bores into each of which a piston is inserted and fixed by front and rear head portions. A driving shaft is installed at the center of the cylinder. A swash plate coupled to the driving shaft is installed in the cylinder where the pistons are installed. As the swash plate rotates, the pistons reciprocate in order in the lengthwise direction of the cylinder.
In the meantime, valve apparatuses for controlling the flow of refrigerant so that the refrigerant is sucked into the cylinder and is discharged to the outside when the refrigerant is compressed by the pistons, is installed between an inner side surface of each of the front and rear head portions and both end portions of the outside of the cylinder.
The refrigerant is sucked into the cylinder by the opening and shutting of the valve apparatus and is compressed by the pistons. The compressed refrigerant is discharged outside the compressor by the valve apparatus.
In the swash plate type compressor, suction chambers by which the refrigerant enters the cylinder after passing the valve apparatus and discharge chambers where the refrigerant compressed by the piston remains are formed at the inner side surfaces of the front and rear head portions. Also, in a fixed volume swash plate type compressor, refrigerant is compressed alternately into the discharge chambers of the front and rear head portions by using dual head pistons where heads are formed in the opposite sides and is discharged. The refrigerant discharged into the discharge chamber of the front head portion is transferred to the rear head portion through a discharge passageway formed between the bores of the cylinder. Here, the refrigerant transferred to the rear head portion is discharged together with the refrigerant discharged from the rear head portion through a discharge port directly connected to the rear head portion, or is discharged through a discharge port of a muffler portion via the muffler portion to an external refrigerant circuit out of the compressor.
Conventionally, since only one discharge passageway through which the refrigerant is transferred from the front head portion to the rear head portion is formed at the upper side of the cylinder, there has been a limit in smoothly transferring the compressed refrigerant from the front head portion.
Also, in an air conditioning system adopting the compressor having the above structure, when a daily temperature range is great, refrigerant in a liquid state may flows in the compressor due to the difference in temperature between a compressor, a condenser, and an evaporator. When the refrigerant in a liquid state enters the compressor, a liquid compression noise is generated at the initial driving of the system. In this case, since the liquid refrigerant compressed in the front head portion is not effectively discharged in the above compressor, noise is not reduced.
To reduce the noise due to the liquid refrigerant, an apparatus such as a solenoid valve for preventing the entrance of the liquid refrigerant into the compressor is provided. However, such an apparatus is expensive and, in the case of malfunction, circulation in the air conditioning system becomes worse and may exert an bad influence on a normal operation.
Japanese Patent Publication No. hei 10-9134 discloses a compressor in which the structure of a muffler is improved so that pulsation of pressure of the refrigerant sucked and discharged is reduced. In this compressor, since only a discharge passageway connecting the discharge chambers of the front and rear head portions are provided, the above-described limit exists.